Crude oil from geological formations commonly contains solids, typically as one or more of waxes, asphaltenes, sulfur, minerals (e.g., scale), and hydrates. When crude oil is transported via pipeline, e.g., from a geological formation to a wellhead or from a wellhead or a storage vessel to a refinery via pipeline, changes in the pressure, temperature, composition, etc. (or other parameters of the flowing crude oil) can lead to deposition of solids on the pipe walls and surfaces. The deposition of these solids from the crude oil onto the interior surfaces of the pipes can have a drastic and negative impact on the oil flow through these pipes.
Asphaltenes, in particular, make up one of the most polar fractions of crude oil, and often will precipitate and deposit on pipe surfaces upon an external stress, such as temperature, pressure and/or compositional changes in the oil (resulting from blending or physical/chemical processing). Asphaltene deposits can plug downhole tubulars, well-bores, choke off pipes and interfere with the functioning of separator equipment.
Traditionally, in the petroleum industry, the problems caused by the deposition of asphaltenes have been controlled by use of asphaltene inhibitors and/or dispersants. Assessment of inhibitor effectiveness has traditionally included down-hole processes, complicated and/or costly lab techniques or non-deposition based methods. Screening through such processes is generally slow and only allows for the screening of one or a few asphaltene inhibitors at a time, or possibly even irrelevant when precipitation-based methods are used. The depositions methods developed to date are too cumbersome and/or costly to make high throughput screening practical.
The asphaltene dispersancy test is currently the industry standard for asphaltene inhibitor evaluation and selection. The test, however, is a precipitation test and gives no information about deposition. Other available tests are expensive for even a single data point, require large quantities of crude oil, and/or take at least several hours to complete. Thus, there exists a need for a reliable, fast, and cost-effective method to assess asphaltene inhibitor efficacy.